Some of Britain's demands for EU reform are acceptable, Polish Prime Minister Beata Szydlo said on Thursday, but added there was no agreement yet on Prime Minister David Cameron's push to curb welfare payments to EU migrants.

Cameron has promised to reform Britain's relationship with the 28-member bloc before a membership referendum by the end of 2017 but his welfare demands have proved most problematic, particularly among eastern European member states.

Szydlo said Poland wanted Britain to remain in the European Union and would do everything to support the country.

"There are proposals from the British government, which are without discussions acceptable for us," Szydlo told a joint news conference with Cameron in Warsaw after a meeting to discuss the British renegotiation.

"There are issues on which there is not a full agreement between us ... This is, among others, the issue of welfare benefits."

Szydlo did not answer when asked by a British journalist whether Poland would ever accept Cameron's proposal for a four-year ban on EU migrants receiving some benefits in Britain.

The British leader said the problem of migration flows and the pressure they put on public services needed to be addressed and the pair had agreed to work together to find a solution.

"I believe with the type of political will I have seen here in Poland we can find a way," he said.